Bearing member



May 28, 1940. F. H. GIVEN BEARING MEMBER Filed Sept. 14, 1938 v Patented May as, 1940 PATENT OFFICE BEARING MEMBER Fred H. Given. Hagerstown, Ind., asslgnor to The Perfect Circle Company, Hagerstown, Ind,

a corporation of Indiana Application September 14, 1938, Serial No. 229,890

6 Claims. (Cl. 308-241) My invention relates to improvements in bearing members and more particularly to hearing members formed of ierrous metal and adapted to have frictional sliding contact, either rotational or reciprocating, with other parts, which iric-' tional contact would ordinarily subject the bearing members to appreciable wear. The invention has particular application to bearing parts of internal combustion engines and as examples of such bearing parts, I mention crank shaft bearings. tappets, cylinder walls, pistons, piston pins, and the like.

More particularly, I form on the bearing members a coating 01' iron oxide of the character described hereinafter, the coating being of such depth as to overcome scui'flng or scoring or uppreciable wear in service and being formed by the processes described herein.

I have illustrated two embodiments oi the invention in the accompanying drawing, wherein:

Fig. 1 is a longitudinal section taken through a shaft bearing;

Fig. 2 is a section through a valve mechanism; and

Fig. 3 is an enlarged view of part of the valve tappet which is shown partially in section to illustrate the oxide coating.

As shown in Fig. 1, the bearing member 2,

which may be of the usual or any desired contour and which is formed of ferrous metal such as cast iron, supports the bearing portion 3 of the shaft 4 which may be the crank shaft of an internal combustion engine, ior example. I have shown, somewhat exaggeratedly, a coating 5 oi substantially pure black magnetic oxide (FeaOr or ierroso-ferric oxide) on the bearing member 2-.

As shown in Fig. 2, the stem 'i of the valve 8 is adapted to reciprocate in a bearing sleeve 9, and the lower end of the valve stem engages an adjustable nut I 0 on a valve tappet i. A cam II on the cam shaft i 2 engages the tappet to actuate it and the valve.

In Fig. 3, I have shown the tappet as provided with a coating 6 01' iron oxide. It will be observed that in this instance the coating 8 is illustrated as comprising two films or layers, the inner film being black in color and the outer film being gray in color, whereas in Fig. 1 the coating is shown as comprising a single black film.

In order better to explain the characteristics of and diiierences between the two coatings, I will describe here the processes by which they are formed.

The bearing members, which are otherwise finished, are placed in a heating or oxidizing chamber of a furnace, the chamber being adapted to be entirely closed against the atmosphere. When the temperature in the closed oxidizing chamber ranges from 600 F. to 850 F. superheated steam or water is injected into the chamber or water, dripping into a flash coil within the chamber, is changed to steam, which causes the chamher to be purged of air through a vent valve. The steam may be circulated by a fan or any other suitable means. The temperature to which the bearing members are heated and the time such temperature is maintained should be such as to give an oxide coating of the minimum desired thickness. An oxide coating having a thickness of about .0003" is formed by heating the bearing members to a temperature of about 1020* F. and maintaining such temperature for a period of about 30 minutes and an oxide coating having a thickness of about .0010" is formed by heating the bearing members to a temperature of about 1300 F. and maintaining such temperature for 'a period of about 30 minutes. To form coatings having a thickness between .0003" and .0010" the bearing members are heated to the desired intermediate temperature and such temperature is maintained for a period of about 30 minutes.

If the bearing members are now permitted to cool to below 600 F. before being withdrawn from the steam, the permanent coating on the bearing :2

members will consist of a single film or layer of substantially pure hard, granular, black magnetic oxide having a very intimate union with the metal. In place of cooling the bearing to a temperature below 600 F. before withdrawal from the steam, the hearing may be withdrawn from the oxidizing chamber to a chamber filled with steam or an inert gas.

The film formed as above explained is that illustrated on the bearing 2 in Fig, 1. g

If the bearing members are removed from the oxidizing chamber before they are partially cooled and then subjected to the atmosphere, the two film coating, as shown on the valve tappet' in Fig. 3, will result. 'The inner black film is formed of substantially pure, hard, black magnetic oxide. -The outer film, which is gray in color, is a little softer than the inner film but it is still somewhat hard and granular. It is diilicult to definitely analyze the outer film, but it seems to be very similar in composition to the inner film. The two films may be either pseudomorphic or allotropic forms of oxide, developing under the diii'erent conditions described.

I find that with the two film coating just de- 2" I .v r

scribd, the black inner film, which I know a substantially pure black magnetic omele, has substantially the same thickness as the outer gray film and this is important to obtain the best results when the two film coating is used.

The required depth of black magnetic oxide film in either case depends upon the load and speed requirements of the bearing member and the environment and-conditions of use of the member. Too thick a filmwill not only the cross section of the bearing member but the film itself will break off since it is quite brittle. On the other hand, too thin a film will not be sufficient to accomplish the object of the invention. It should be of such depth as to substantially prevent scumng or scoring during the normal life of the bearing member under proper operating conditions. The coating on the bearings for a crank shaft of an automobile engine, for example, should not be less than .0003" and preferably .0010. In other specific applications, fairly satisfactory results have been obtained with bearing surfaces having a coating as thin as 0.00015".

The action of the oxide coating in accomplishing its especially advantageous results is somewhat dimcult to account for and explain. Apparently, the hard, granular texture of the coating and, particularly of the black layer or him is in itself resistant to we'ar'and abrasion. The particles are quite small and durable in a brittle sense and do not cause undue disruption of the mutually frictional surfaces. The fine and durable nature of the oxide particles also appears to create a progressive polishing of the contacting friction surfaces without causing substantial wear. This polishing or mild honing action keeps the surfaces mutually parallel, prevents formation of abrading projections thereon and contributes to good lubrication and minimum friction therebetween. In some instances I have found that the oxide coating aloneis a sufficient lubricating medium. j It will be understood that both of the cooperating bearing members, such for example as the valve tappet and cam i2, may be given the oxide coating though this usually is notnecessary. I have found that where only one of the bearing members has been treated, as I have explained, the oxide coating thereon conditions progressively the contact surface of the other member, some of the 'oxide being actually transferred from the one to the other during service.

with the two film oxide coating, the one film being black and the other one gray, as above explained, the outer softer film tends to wear away during the "run in" period. This may be beneficial. The black inner layer should be substantially as thick as the outer layer and of sumcient thickness to last during the normal use of the bearing member under proper operating,

conditions. I

The bearing sleeve '9 (Fig. 2) may be given either oxide coating which I have described above.

I claim:

1. A hearing member of the class described formed of ferrous metal and provided with a bearing coating comprising a film of hard, granular, ferroso-ferric oxide having intimate union with the metal.

2. A bearing member of the class described formed of ferrous metal and provided with a bearing coating including a film of substantially pure, hard, granular. Feaot having intimate union with the metal and having a thickness of at least .00015".

3. A bearing member of the class described formed of ferrous metal and provided with a bearing coating consisting of substantially pure,

hard, granular, ferrcso-ferrlc oxide having intimate union with the metal and having a thickness of approximately .0003".

4.-A bearing member of the class described formed of ferrous metal. and provided with a bearing coating formed of two intimately united films, the inner him being formed of substantially pure, hard, granular, ferroso-ferric oxide having intimate union with the metal and the outer film being formed of a-softer and gray iron oxide.

5. Abearing member of the class described formed of ferrous 'metal and provided with a bearing coating comprising two intimately united superposed oxide films, at least one of said films consisting of substantially pure R304.

6. A bearing member of the class described formed of ferrous metal and provided with a bearing coating comprising two intimately united superposed oxide films, the aggregate thickness of said films being at least 0.00015", and at least one of said films consisting substantially entirely of F8304.

. FRED H. GIVEN. 

